Exploring the Huky 500 Coffee Roaster, Part II

Discuss roast levels and profiles for espresso, equipment for roasting coffee.
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Postby slickrock » Feb 15, 2012, 6:55 am

Back to Part 1 of Review

Forward to Part 3 of review

Exploring the Huky 500 Part 2:


This part of the review covers the solid drum design and customizations need for the Huky 500 to operate properly with my stovetop range. Since this part has integration specifics, which may or may not be relevant for your intended setup, I'm deferring overall roaster operation and profiling topics to Part 3, that way you can easily skip this part in favor of the more interesting operational characteristics of this roaster.

Going Solid-Drum

The current Huky 500 design is largely built around a portable infrared stove platform as a heat source, which implies that the primary way the beans are roasted in the Huky is via direct irradiation. That is probably why Kuanho offers perforated drums as standard equipment for the Huky, where, similar to the Hottop, the beans are irradiated by the heat source through the drum perforations. This approach appears similar to the old Burns-style way of drum roasting from the 1930's (Jim's comment), basically directly radiating the beans with heat and the drum perforation provides natural ventilation (albeit with the Hottop and the Huky, there is forced ventilation). The Huky design also provides a nifty shutter control with a handle , that when pulled in and out, can either expose or occluded the drum perforations and control how the level of direct irradiation of the beans by the IR burner. Kuanho recommends opening the shutter during the drying phase of the roast, effectively speeding up this phase, and then closing the shutter during the remainder of the roast.

But at the outset, my desire was to acquire a solid drum roaster, which typically uses a combination of drum heat radiation and forced air convection. Could the Huky 500 be successfully converted into a Probat-style roaster, like the Quest? Outfitting the roaster with a solid drum is good start, but there are other factors that need to be in place as well, such as strong and even forced air ventilation and proper heat control. And what about the shutter control? How would it even work with a solid drum? I wanted to make sure that the solid drum would work more affectively with the whole apparatus, so I asked for the following customizations:

    1. Dual shutters: the stock roaster has a single shutter to control direct or indirect radiation by exposing or hiding the holes in the perforated drum, as explained above. However with a solid drum, the shutter would be rendered useless since there would be no holes to cover up. What I instead requested was to convert the setup to a heat diffuser and used the shutter to control the degree of diffusion from the heat source. This was accomplished by having Kuanho add a second stationary shutter between the drum and the moveable shutter (see photos). With the shutter open, heat would be allowed to directly radiate the drum for pre-heating and for the charge/drying stage of the roast.


    With the shutter closed, the apparatus would diffuse direct heat radiation, creating a more indirect exposure.


    For open flame heat sources like in my setup, convective hot air (in theory) would flow around the backside of the roaster into the perforated back of the drum through the bean mass and then out the chimney (image below illustrates flow if drum is solid, although photo is of perforated drum) .


    For setups that use an IR burner, the shutter could be used less for directing hot air and more as a straight-up heat diffuser since IR burners can pump out a lot of radiation. Keep in mind that this was perhaps the most customized request Kuanho fulfilled for me, and was a bit of a prototype effort in this regard.

    2. Faster drum speed: The stock motor rotates the drum at 50RPM, which may be adequate for a directly-radiated perforated drum, but I had my doubts about this speed being adequate for a solid drum. It seems to me that there would be less irradiated heating with a solid drum (no direct burner IR), where more agitation would be required for large bean charges to increase exposure to drum surface. To combat this, I ordered an extra motor that runs at 73 RPM fixed. This value is under the Max RPM-10% rule: the maximum agitation RPM for the Huky drum diameter is 84.6 and less 10% leaves 76.1 RPM (enough headroom not to worry about beans sticking to the sides). Still, it would be nice to a variable speed motor for this purpose, but the variable speed DC geared motor was not available from the OEM. It is possible to add some circuitry with a power transistor to create a variable speed setup (in a Heath Kit style effort), but the power transistors were far more expensive than the motor itself. So its staying fixed speed for now.

    3. Tighter gap clearances: I asked Kuanho to tighten up the clearances to 0.5 mm (from about 1-1.5mm) between the drum and front faceplate so the forced air ventilation would travel primarily through the back of the drum instead of leak through the gap.

    4. More ventilation holes: I asked Kuanho to add more holes on the back end of solid drum, more so than what was pictured here. Basically, this was done to aid convective circulation of air through the bean mass.

With the above configuration options, I basically chose to do something different with the Huky: to convert the roaster into a solid drum roaster and use open gas flame (versus IR) as a heat source (from Bluestar range). This configuration also allows me to put the powerful fan of the Huky to good use through the circulation of heated air (from the open gas flame) through beans along a single path along the length of the drum: from the back of the drum where the holes exist, then along the drum to the exit chimney, improving ventilation flow. In other words, these modifications allow the employ of convection as well as radiation (directly from heated the drum) to roast the beans.

Integration with the Heat Source

By design, Huky 500 is not a self-contained roasting appliance, but instead requires and external heat source for roasting. As stated earlier, Huky 500 design is built around a portable infrared stove platform as a heat source, but this integration this goes further than necessary and makes several assumption about what burner will be used. In fact, the roaster dimensions, support feet, and fixed exhaust piping apparatus assume the particular style of portable burner seen in the photograph be used with the Huky. Kuanho offers this burner for sale for a reasonable price, and if one purchases it, it would greatly simplify the heat integration and setup of the roaster immensely, and none of what follows would be needed if I chose to use that portable burner (or similar) for my setup.

But my intention is to use the roaster on my own Bluestar cooking range, so I knew extra integration steps must to be taken to make sure the Huky 500 would work with my setup. The main issue is that configuration assumes that the height of the roaster is offset by the height of the burner (offset by about 90 mm as seen in the following diagram),


where the fan sits below the grate on a tabletop and the roaster is sitting atop the portable burner. This configuration would be unworkable for range-top heating because the burner is recessed under the grate, where both the fan/tray stack and the roaster itself should sit at the same level. Therefore I requested customizations and/or performed the following changes to integrate the Huky with the Bluestar range:

    1. Exhaust pipe height made adjustable: the standard exhaust pipe fitting has a fixed (non-adjustable) height and has two collars that are spot-welded together, to accommodate the offset of the portable burner. To remedy this, I asked Kuanho to not spot-weld the bottom collar that connects to the funnel, but rather leave it to float freely. This would allow me to adjust the height of the exhaust pipe as needed to align the height of the roaster with the height of the fan, both of which would rest on top of my gas range (see diagram below).


    Once adjusted, I fastened the position of the collar by drilling and tapping a hole in the collar for a small set screw that could be tightened to fix the position.


    2. Added adjustable Feet for the Fan: the stock fan setup has thick-gauge metal wire spot-welded to the bottom fan grill to serve as feet for the fan, at a fixed height of 80 mm. I requested from Kuanho a bottom grill without the feet welded on. To elevate the fan I went to the hardware store and purchased an assortment of aluminum posts of different lengths that can be screwed into each and stacked at various heights to offset fan/tray height as needed to clear the lip of the roaster door.


    3. Added metal support feet to the roaster: the stock Huky roaster comes with heat resistant rubber feet that are designed to sit in the recessed area of the portable IR burner where there is less heat present. I had some reservations about this for my setup because the roaster would instead sit atop the range burner with the rubber feet in direct in contact with the very hot cooking grate. Well, it turned out that my trepidations were prescient because those feet combusted in plume of smoke and flame during my very first roast!


    To remedy this I went back to the hardware store an bought various screws, washers, and brass bushings and made metal support feet for the roaster (see photo below). The new metal feet also added an extra centimeter of roaster height to provide added clearance for the tray/fan setup.


    4. Added MET temperature probe: The stock Huky Roaster comes with an analog temperature gauge to measure ET within the drum and a digital K thermocouple to measure BT. However, the Huky does not come with a MET probe. Popularized by Jim's usage of a temperature probe located outside the drum (of his Quest M3) to measure the direct temperature of the drum (outside the influence of the bean mass and forced air ventilation), the MET probe provides a proxy for the maximum allowable temperature that the roaster can be held at without scorching the beans. This is of particular importance for the Huky since scorching is clear possibility when you have a gas burner as a high-power heat source in place of an electrical heating element with limited BTU/hr output.

    I made this modification by drilling a hole in the faceplate of the roaster so that the probe would sit just above the roasting drum. I chose to place the probe on the top left side because I wanted to move the analog gauge to that position and it was easier to sight the gauge from that position for my setup (the right side is actually less crowded, and would be a better place to put the MET probe if I chose to use a permanent digital thermocouple there).


    I used a 1/4NPT-to-1/8NPT pipe adapter and mounted the brass adapter onto the faceplate. Doing so allowed me to move the analog gauge to that location (the analog gauge has 1/4NPT threading). I also obtained a 1/4NPT brass plug and drilled a hole in the center of it and tapped to fit the extra digital temperature probe I purchased from Kuanho [see photo].


    This configuration allows me to switch out the analog gauge with the digital probe (and vice versa) at will without having to tear down the roaster to do so. Note that I made this modification some time after I began roasting with Huky, but I'm including it in this list because it really does provide a good metric to the roasting process (discussed in Part 3).

I realize that the protracted discussion above is a bit heavy to wade through but I do feel it sets the stage for a better understanding of the operation of the Huky 500 in the roasting process, and how my particular configuration may add or subtract from that process. Next up will be Part 3 of the review and will conclude by covering roasting results and detailed operation of the Huky 500.

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Forward to Part 3 of review
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Postby tekomino » Feb 15, 2012, 10:27 am

Dang, that's almost completely different roaster from stock one... :D
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Postby mariowar » Feb 15, 2012, 12:07 pm

I understand that there is no website advertising this roast....

How mucho did you pay for it including shipping to the USA?


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Postby hankua » Feb 15, 2012, 12:11 pm

Great job Joel! Mr. Li is going to be busy this year. :D

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Postby JWilliams » Feb 16, 2012, 12:53 pm

Thanks Joel for posting!!! Can't wait for part 3...

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Postby JK » Feb 17, 2012, 5:21 am

Can I have the contact info for maker?
I'm thinking of buy one..

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Postby slickrock » Mar 11, 2012, 6:48 am

Just added Part 3 of the review: Exploring the Huky 500 Coffee Roaster, Part III
Never mistake a clear view for a short distance.